The present invention relates to a screen for removing foreign substances from a raw material such as, for example, used paper, pulp and the like, and more specifically, to a composite type screen including a single machine main body provided with a plurality of screen members disposed therein.
2. Description of the Related Art
As shown in FIG. 4, a conventional composite type screen is arranged such that a first screen member, e.g., a screen plate 101 having round holes, is disposed in a cylindrical machine main body 100 so that the interior of the machine main body 100 is divided into a primary processing chamber A and a secondary processing chamber B. An opening on the primary processing chamber A side of the machine main body 100 is sealed with a lid 100A.
A motor 102 and a bearing 103 are disposed outside the machine main body 100. A rotary shaft 104 pivotally supported by the bearing 103 is inserted into the machine main body 100. The rotating force of the motor 102 is transmitted to the rotary shaft 104 through a belt 105.
The rotary shaft 104 has a first stirring member, e.g., an impeller 106 mounted thereon in the first processing chamber A side thereof and a second stirring member, e.g., a rotor 107 mounted thereon in the first processing chamber B side thereof.
The second processing chamber B includes a second cylindrical screen member, e.g., a cylindrical basket screen 108 disposed therein. The basket screen 108 has a function for capturing foreign substances smaller than the holes defined by the screen plate 101.
Further, the gap between the central hole (not shown) of the screen plate 10t and the rotary shaft 104 is sealed by a seal member 109 such as a gland packing and the like to prevent a raw material, e.g. a paper material in the primary chamber A from entering the second processing chamber B without passing through the screen plate 101.
The gap between the shaft hole (not shown) of the machine main body 100 and the rotary shaft 104 is sealed by a mechanical seal and the like to prevent the leakage of the paper material.
The machine main body 100 includes a raw material inlet, e.g. a paper material inlet 111 and a primary discharge port 112 each being connected to the primary processing chamber A as well as a paper material outlet 113 and a secondary discharge port 114 each being connected to the secondary processing chamber B.
The paper material charged into the primary processing chamber A under pressure from the paper material inlet 111 is stirred and unravelled by the impeller 106 being rotated. The unravelled paper material passes through the screen plate 101 and the foreign substances contained in the paper material are captured by the screen plate 101. The captured foreign substances are discharged from the primary discharge port 112.
The paper material which has been roughly selected when passing through the screen plate 101 also passes through the basket screen 108 while being stirred by the rotor 107 being rotated in the secondary processing chamber B.
The paper material which has been finely selected and separated from the foreign substances thereof when it passes through the basket screen 108 is discharged to the outside of the machine main body 100 from the paper material outlet 113 and the removed foreign substances are discharged from the secondary discharge port 114.
As described above, the paper material is differently processed in the primary processing chamber A and the secondary processing chamber B. Further, the machine main body 100 arranged as a single body is made compact by providing both the screen plate 101 and basket screen 108 therein.
Nevertheless, the prior art has the following problems because the single rotary shaft 104 is disposed in the state that it passes through the central portion of the screen plate 101 as well as both the impeller 106 and rotor 107 are mounted to the rotary shaft 104:
(1) since the impeller 106 and rotor 107 rotate at the same number of rotation at all times, the foreign substance removing functions of the first processing chamber A and second processing chamber B cannot be separately controlled in accordance with the variation of conditions such as a kind of a paper material, and the like; PA1 (2) since the seal member 109 is interposed between the screen plate 101 and the rotary shaft 104, the number of parts is increased and a manufacturing cost is increased; and PA1 (3) since the rotary shaft 104 and seal member 109 are provided at the central portion of the screen plate 101, the area of the screen plate 101 through which a paper material passes is reduced and thus the foreign substance removing function of the screen plate 101 is lowered.